Finasteride: prostate, hair loss and the post-finasteride syndrome explained honestly

Finasteride is an unusual medicine: the same active ingredient is used in a higher dose against an enlarged prostate and in a lower dose against hereditary hair loss. Both work via the same principle. At the same time, finasteride is under discussion because of possible persistent side effects, the so-called post-finasteride syndrome, a topic that many sources prefer to keep quiet about. This guide explains honestly and factually how finasteride works, why there are two doses and what the state of science on the disputed side effects looks like. It does not replace medical advice but helps you weigh benefit and risks realistically.

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At a glance

  • Finasteride is a 5-alpha-reductase inhibitor that lowers the hormone DHT, which plays a role in prostate growth and hair loss.
  • In the 5 mg dose it shrinks the prostate; in the 1 mg dose it is used against hereditary hair loss.
  • Even 1 mg lowers the DHT level by around 70 percent, almost as strongly as 5 mg.
  • Sexual side effects are mostly temporary but can persist with a subgroup: the post-finasteride syndrome.
  • Finasteride lowers the PSA value by about half, which is to be considered with prostate cancer early detection.

What is finasteride and how does it work?

Finasteride belongs to the group of 5-alpha-reductase inhibitors. To understand its effect, a look at a hormone called DHT, short for dihydrotestosterone, helps. DHT arises in the body from the better-known hormone testosterone, with the help of an enzyme, the 5-alpha-reductase. DHT is a clearly stronger androgen than testosterone and plays a role in several places, among others in the growth of the prostate and in hereditary hair loss.

Exactly here is where finasteride comes in. It blocks the enzyme 5-alpha-reductase and thereby prevents testosterone from being converted into DHT on a large scale. The result is that the DHT level in the blood falls clearly, by about 70 percent. Because DHT drives both the prostate growth and the hair loss, both can be influenced via this one mechanism: the prostate can shrink and the hair loss slow down. Important is that finasteride works slowly, often only over months, and only as long as it is taken. After stopping, the original processes mostly return.

One active ingredient, two very different goals

The special thing about finasteride is that the same mechanism addresses two quite different problems. With the prostate it is about the shrinking of an enlarged organ; with hair loss about the preservation of the hair roots. Both rest on the fact that less DHT is formed. Exactly for this reason finasteride also only works where DHT plays a role and is not a general hair growth agent or prostate miracle cure. The use should always fit the respective diagnosis.

Why 1 mg and 5 mg? The two doses

Finasteride exists in two main doses that stand for the two areas of use. The 5 mg tablet is used with the benign prostate enlargement, the 1 mg tablet with hereditary hair loss. At first glance this seems confusing because the same active ingredient is prescribed in such different amounts. The reason behind it is, however, medically interesting and well documented.

Investigations have shown that even 1 mg finasteride lowers the DHT level in the blood by around 70 percent. An increase to 5 mg brings only a small additional fall of the DHT. For the hair loss this strong lowering is already enough, which is why the low 1 mg dose is chosen here, to keep the amount of active ingredient and thereby the side effect risk as low as possible. With the prostate, the 5 mg dose has proven the most effective in studies with good tolerability, because here a lowering of DHT in the prostate tissue that is as complete as possible is the goal. Which dose is sensible in the individual case depends on the diagnosis and is determined medically. An unauthorised increase of the hair loss dose, by the way, brings no better effect but only a higher risk of side effects without additional benefit.

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Finasteride with the prostate and with hair loss

With the benign prostate enlargement, DHT contributes to the excessive growth of the prostate. By lowering the DHT level, finasteride actually lets the prostate shrink over several months, in studies mostly by about a fifth of its volume. As a result the complaints with urination improve, the urine stream becomes stronger, and in the long term the risk of an acute urinary retention or a prostate operation falls. Unlike an alpha blocker, which only relaxes the muscle, finasteride thereby tackles the actual cause, the growth, but needs patience for this, because the effect only builds up over three to six months.

With hereditary hair loss, the androgenetic alopecia, the hair roots are genetically sensitive to DHT. The hormone shortens the growth phase of the hairs; the hairs become thinner and finally fall out. Finasteride lowers the DHT level and thereby takes away from the hair roots part of this harmful stimulus. According to studies, the progressive hair loss can be stopped with about 80 percent of users and with a part even an increased growth achieved. Here too it applies: the effect builds up slowly over months and only lasts as long as the agent is taken. If finasteride is stopped, the hair loss as a rule returns within a few months.

The post-finasteride syndrome: honest instead of keeping quiet

Let us come to the topic that many sources prefer to leave out but that belongs to an honest explanation: the so-called post-finasteride syndrome, PFS for short. This is the name for complaints that can persist with a part of users even after stopping finasteride. These include sexual disorders such as a reduced libido, erection and ejaculation problems as well as psychological symptoms such as depression, anxiety and concentration disorders. Important for classification: most sexual side effects with finasteride are temporary and recede after stopping. With PFS it is about a subgroup with which the complaints can apparently last long, partly over years.

How honest is the data situation? It is disputed, but it is to be taken seriously. Many studies on it have methodological weaknesses, for example small case numbers or the risk of distortions. Exactly for this reason the exact frequency is unclear. One of the few cohort studies found persistent complaints with under one percent of the young users. Despite the uncertainties, the British drug authority, for example, came after examination of many case reports to the conclusion that overall there are sufficient indications for a risk of persistent sexual and psychological side effects. In Germany a warning on depressive mood and suicidal thoughts was added to the prescribing information in 2017, and the manufacturers sent out an official safety letter. Interestingly, such complaints are reported more often by men who take finasteride against hair loss than by men with prostate treatment, without the cause for this being clarified. Possible explanations range from the younger age and the higher attention of this group to still ununderstood biological differences. Exactly this uncertainty is the reason why the topic is discussed so controversially in the professional world and why a blanket trivialisation is just as inappropriate as a blanket scaremongering.

Above all with hair loss: weigh benefit and risk

Precisely when finasteride is to be taken only against hair loss, that is not against a burdensome disease, an honest weighing-up is important. Some professional bodies assess the benefit-harm ratio in this situation critically, because it is about a cosmetic goal facing a rare but possibly long-lasting risk. Have yourself openly informed about possible sexual and psychological side effects before the start and decide consciously. If depressive moods or suicidal thoughts occur during the intake, seek medical help immediately.

Further side effects and the PSA value

The best-known side effects of finasteride concern the sexual function: a reduced desire, erection disorders and ejaculation disorders. They occur with a smaller part of users and are in most cases temporary. Less often a feeling of tension or an enlargement of the breast occurs. An important safety note concerns women: pregnant women or women who could become pregnant must not take finasteride and also not touch broken or disintegrated tablets, because the active ingredient can disturb the development of the sexual organs of a male fetus.

A point that is often overlooked but is medically very important concerns the PSA value. PSA is a blood test that is used with the early detection of prostate cancer. Finasteride lowers the PSA value by about half. This means: anyone who takes finasteride has an artificially lower value that can mask an actually conspicuous finding. So that the value is classified correctly, your medical practice must without fail know that you take finasteride, because then the measured value is interpreted accordingly, mostly about doubled. Therefore state the intake with every PSA determination. This point is not a detail in the margin but can in an emergency decide whether a serious disease is recognised in time. A simple note on the finasteride intake is enough so that the value is assessed correctly.

Aspect Finasteride (5-ARI) Tamsulosin (alpha blocker)
Effect shrinks the prostate relaxes the muscle
Onset of effect slow, over months quick, often in days
Approach tackles the cause eases only the symptoms
Typical side effect sexual disorders, PFS debate retrograde ejaculation, dizziness

Finasteride or tamsulosin?

With the treatment of the enlarged prostate, two very different strategies are available with finasteride and tamsulosin. Tamsulosin is an alpha blocker that relaxes the muscle in the prostate and bladder neck and eases the complaints quickly without shrinking the prostate. Finasteride, on the other hand, tackles the cause and lets the prostate shrink over months but works more slowly. Put simply, tamsulosin works quickly on the symptoms and finasteride long-term on the size.

Which strategy is sensible depends on the complaints and the prostate size. With a clearly enlarged prostate, the size-reducing approach of finasteride can be particularly sensible, while with above all bothersome symptoms the quick-acting alpha blocker is often preferred. With pronounced complaints, both active ingredients are sometimes combined to connect the quick and the causal effect, which can, however, increase the risk of sexual side effects. This weighing-up should always be made together with the medical practice.

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In sum, finasteride is an effective medicine that tackles the cause with an enlarged prostate and helps many men with hereditary hair loss. An honest use means, however, knowing both sides: the clear benefit and the disputed but to-be-taken-seriously risk of persistent side effects, above all when the goal is only the hair. Important also is to state the intake with every PSA determination. With a prostate enlargement, finasteride is a causal option, often in comparison or in combination with tamsulosin. Anyone who considers finasteride against hair loss should weigh benefit and risk particularly consciously.

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Add your medicines to brite for free and take a clear overview with you to the appointment. This way you can specifically address finasteride, the PSA value and possible side effects and not forget anything important.

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Frequently asked questions about finasteride

Finasteride is a 5-alpha-reductase inhibitor. It blocks an enzyme that converts testosterone into the stronger hormone DHT. DHT plays a central role with prostate enlargement and hereditary hair loss. By lowering the DHT level, finasteride can shrink the prostate and stop the hair loss. It works slowly over months and only as long as it is taken. Finasteride is prescription only.
The 5 mg dose is used with an enlarged prostate, the 1 mg dose with hereditary hair loss. Even 1 mg lowers the DHT level by about 70 percent, almost as strongly as 5 mg. Therefore the lower dose is enough for the hair loss to keep the amount of active ingredient low. Which dose is sensible depends on the diagnosis and is determined medically.
With hereditary hair loss, the hair roots react sensitively to DHT, which shortens the growth phase. Finasteride lowers the DHT level and takes away from the hair roots part of this influence. According to studies, the hair loss can be stopped with about 80 percent of users, with a part even increased growth achieved. The effect builds up over months and only lasts as long as the agent is taken.
With an enlarged prostate, DHT contributes to the growth. Finasteride lowers the DHT level and lets the prostate shrink over months, mostly by about a fifth. As a result the complaints with urination improve, and the risk of urinary retention or operation falls in the long term. Unlike an alpha blocker it tackles the cause but works more slowly and often needs three to six months.
This is the name for complaints that can persist with a part of users even after stopping, for example sexual disorders as well as depression, anxiety and concentration disorders. Most sexual side effects are temporary, but with a subgroup they can last long. How frequent this is is scientifically not conclusively clarified, but authorities see enough indications for a warning.
The data situation is disputed but to be taken seriously. Many studies have methodological weaknesses such as small case numbers. Nevertheless the British drug authority, for example, sees after examination of many case reports enough indications for a risk. In Germany a warning on depression and suicidal thoughts came into the prescribing information in 2017, with an official safety letter. The exact frequency remains unclear, which is why honest explanation is important.
Best-known are sexual disorders such as reduced desire, erection and ejaculation disorders, mostly temporary. Less often breast tenderness or breast enlargement occurs, depressive moods are also named. Pregnant women must not take finasteride or touch broken tablets, as it can harm a male fetus. With complaints seek medical advice.
Yes. Finasteride lowers the PSA value by about half. The PSA value is used for early detection of prostate cancer; an artificially low value can mask a conspicuous finding. Therefore your medical practice must know that you take finasteride so that the value is classified correctly, mostly about doubled. State the intake with every PSA determination.
Tamsulosin is an alpha blocker that relaxes the muscle and eases the complaints quickly without shrinking the prostate. Finasteride is a 5-alpha-reductase inhibitor that lets the prostate shrink over months and tackles the cause but works more slowly. Tamsulosin works quickly on the symptoms, finasteride long-term on the size. With strong complaints a combination is possible.

Related topics

Sources

  • Urologielehrbuch: finasteride, mechanism, side effects, dosage
  • haarerkrankungen.de: finasteride, DHT lowering and 1 mg dose
  • Drug commission of the German medical profession / Deutsches Ärzteblatt: psychiatric and sexual side effects of finasteride
  • Springer / Gynäkologische Endokrinologie: the post-finasteride syndrome
  • GUAD network: persistent sexual dysfunctions after finasteride (official safety letter)
  • Prostata-Hilfe Deutschland: 5-alpha-reductase inhibitors and PSA value

This guide serves general information and does not replace medical advice, diagnosis or treatment. It contains no dosage recommendation. Finasteride is prescription only. Take it only on medical prescription, state the intake with every PSA determination and seek medical help immediately with depressive mood or suicidal thoughts. This text deals with side effects that can be burdening. If you feel mentally unwell, turn to your medical practice or a counselling service.